'disavow' originates from Old French, specifically the word 'desavouer', where 'des-' meant 'opposite of' and 'avouer' meant 'to acknowledge'.

'desavouer' transformed into the Middle English word 'disavowen', and eventually became the modern English word 'disavow'.

Initially, it meant 'to refuse to acknowledge', and this meaning has largely remained the same in modern usage.